Lab case 387 Interpretation

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Answers:

Question 1:

pH = 7.357, that is within the normal range, towards the acidotic side.

HCO3 = 16.2, that is low. So, we have metabolic acidosis

Next, we need to calculate the compensation and the Anion Gap for this patient.

We use Winter’s formula to get the expected pCO2 that is:

Expected pCO2 = 1.5 x HCO3 +8 (+/- 2). That will give us expected pCO2 of 32.3 (30.3 – 34.3). Here, it can be mild respiratory component, or it is normal as the sample was venous. (We need to get an arterial sample to find out the correct answer for that).

Anion Gap = Na – (Cl+HCO3) = 11 (normal)

So, we have normal anion gap metabolic acidosis NAGMA.

Other abnormal findings:

Na = 127, that is moderate hyponatraemia. However, this patient had high glucose level. High glucose cause pseudohyponatraemia.

To calculate the corrected Na level we use the following formula.

Corrected Na = Measured Na + (Glucose – 5)/3 = 130 mmol/L. That puts Na level for this patient in the mild range.

Hyperkalaemia

Severe hypocalcaemia

High glucose (no ketones given, normal anion gap)

  1. Interpret your findings

These biochemical features are consistent with multiple endocrine dysfunction:

Addison’s disease (low Na, high K, NAGMA)

Uncontrolled Diabetes (check ketones)

Hypocalcaemia

Check Thyroid function (very fast HR)

However, it is important to consider sepsis as a cause. (hypotension, tachycardia, diarrhoea. features on history are suggestive. However, lactate is normal

  1. Examination Features:

(a) Source of infection – thorough head to toe examination, including ENT, chest, abdomen. CXR and UA immediately

(b) Severity of sepsis/ complications – GCS, perfusion, Urine output, Ileus,,, etc.

(c) Features of Addison’s – weight loss, hyperpigmentation

In general, some features of Addison’s include:

  • Muscle weakness and fatigue
  • Weight loss and decreased appetite
  • Darkening of your skin (hyperpigmentation)
  • Low blood pressure, even fainting
  • Salt craving
  • Low blood sugar (hypoglycemia)
  • Nausea, diarrhea or vomiting
  • Muscle or joint pains
  • Irritability
  • Depression
  • Body hair loss or sexual dysfunction in women

(d) Features of hypocalcaemia

“CATS go numb”- Convulsions, Arrhythmias, Tetany and numbness/parasthesias in hands, feet, around mouth and lips.

  • Petechiae, purpura
  • Oral, perioral and acral paraesthesia (early symptom)
  • Carpopedal and generalized tetany
  • Latent tetany
    • Trousseau’s sign
    • Chvostek’s sign
  • Tendon reflexes are hyperactive
  • Life-threatening complications
    • Laryngospasm, brochospasm
    • Cardiac arrhythmias
  • Effects on cardiac output
    • Positive chronotropy
    • Negative inotropy effect
  • ECG – Intermittent QT prolongation – high risk of TdP

Chronic hypocalcaemia – poor dentition, cataracts, papilloedema, ectopic calcification, dementia

(e) Complications of Diabetes:

Retinopathy

Neuropathy

Renal impairment….. etc

  1. Treatment Priorities

Full cardiac monitoring, serial ECG’s, defib pads applied

Resuscitation – as per surviving sepsis – fluids, antibiotics (source control), other – inotropes, monitor response to treatment

Replace Calcium – 10 mls of 10% Ca Gluconate IV

Steroids – hydrocortisone 200 mg IV

Insulin Infusion  (2-4 units/hr)- aim to correct ketoacidosis if present and correct glucose gradually over 2-4 hours